Botanical characterization and authentication of lavender essential oil using its volatile organic compounds and compound-specific carbon and hydrogen isotope ratio analysis

The determination of authenticity and provenance is one of the main issues in high-value natural products such as lavender (L. angustifolia) essential oil. Due to their high value, natural products are often totally or partially substituted with cheaper alternatives. Therefore, it is necessary to accurately characterize the composition of lavender essential oil and its related species, particularly lavandin (L. intermedia) essential oil, which is frequently used as an adulterant. In this study, we analyzed the most distinctive volatile organic compounds (VOCs) and their relative compound-specific stable carbon and hydrogen (delta C-13 and delta H-2) isotope ratios in lavender, lavandin, and commercial lavender essential oil samples using fast GC-MS/MS and GC-IRMS methods and sparse Partial Least Square Discriminant Analysis (sPLS-DA) to classify and verify their botanical origin. For the first time, concentration ranges for 79 VOCs and the delta C-13 and delta H-2 values in 32 VOCs were used to characterize lavender essential oils. sPLS-DA models with either VOCs, delta C-13 and delta H-2, or in combination successfully classify lavender and lavandin with 100% accuracy. VOCs such as camphor, borneol, eucalyptol, alpha-bisabolol, and alpha-pinene were found to be the most important variables for differentiating lavender oil from lavandin. Similarly, delta C-13 in camphor, eucalyptol, trans-beta-ocimene and 3-octanone, and delta H-2 in alpha-terpineol and trans-beta-ocimene and 3-octanone also differentiated lavender and lavandin oil. In addition, we demonstrated that compound-specific delta C-13 and delta H-2 detected the adulteration of natural lavender or lavandin oil if more than 15% of linalool, linalyl acetate, eucalyptol, and alpha-terpineol were of synthetic origin. These preliminary results with sPLS-DA models suggest that VOCs and compound-specific delta C-13 and delta H-2 can be a promising tool for the botanical classification of lavender essential oil and the detection of possible adulteration with synthetic compounds.

Automated summary

This study analyzes the volatile organic compounds (VOCs) and their stable carbon and hydrogen isotopes in lavender essential oil, lavandin essential oil, and commercial lavender essential oil samples to classify and verify their botanical origin. The results show that VOCs and compound-specific stable isotopes can be a promising tool for the botanical classification of lavender essential oil and the detection of possible adulteration with synthetic compounds.